Method for repairing reflective optical elements for EUV lithography

Abstract

A cost-effective method for repairing reflective optical elements for EUV lithography. These optical elements (60) have a substrate (61) and a coating (62) that reflects at a working wavelength in the range between 5 nm and 20 nm and is damaged as a result of formation of hydrogen bubbles. The method includes: localizing a damaged area (63, 64, 65, 66) in the coating (62) and covering the damaged area (63, 64, 65, 66) with one or more materials having low hydrogen permeability by applying a cover element to the damaged area. The cover element is formed of a surface structure, a convex or concave surface, or a coating corresponding to the coating of the reflective optical element, or a combination thereof. The method is particularly suitable for collector mirrors (70) for EUV lithography. After the repair, the optical elements have cover elements (71, 72, 73).

What is claimed is: 
     
       1. A method for repairing delamination or blistering of a coating of a reflective optical element for extreme ultraviolet (EUV) lithography which comprises a substrate and the coating that reflects at an operating wavelength in a range of between 5 nm and 20 nm, comprising:
 localizing a damaged location in the coating caused by the delamination or blistering of the coating of the reflective optical element; and 
 covering the damaged location with one or more materials by applying a covering element localized to the damaged location; 
 wherein arranged on the covering element is one or more of a surface structure, a convex or concave surface or a covering element coating corresponding to the coating of the reflective optical element. 
 
     
     
       2. The method as claimed in  claim 1 , wherein the covering element is secured on the coating with adhesive. 
     
     
       3. The method as claimed in  claim 1 , wherein the covering element is embodied as a film or a covering unit. 
     
     
       4. The method as claimed in  claim 1 , wherein the covering element comprises one or more materials of the group metal, steel, high-grade steel, Invar, aluminum, molybdenum, tantalum, niobium, silicon, titanium, zirconium, hafnium, scandium, yttrium, lanthanum, cerium, copper, silver, gold, platinum, rhodium, palladium, ruthenium, glass, ceramic and aluminum oxide. 
     
     
       5. The method as claimed in  claim 1 , wherein said covering comprises applying a covering coating to the damaged location. 
     
     
       6. The method as claimed in  claim 5 , wherein the covering coating is applied by tin plating, gold plating, electroplating, oxidation, nitriding and/or deposition by atmospheric pressure plasma. 
     
     
       7. The method as claimed in  claim 6 , wherein said applying comprises:
 applying a metal layer comprising gold, platinum, rhodium, palladium, ruthenium, molybdenum, tantalum, niobium, silicon, titanium, zirconium, hafnium, aluminum, scandium, yttrium, lanthanum and/or cerium by electroplating as the covering coating, or 
 applying a covering coating comprising one or more of the group molybdenum, tantalum, niobium, silicon, titanium, zirconium, hafnium, aluminum, scandium, yttrium, lanthanum, cerium, oxides thereof, nitrides thereof, carbides thereof, borides thereof, gold, platinum, rhodium, palladium, ruthenium, carbon, boron carbide and boron nitride by atmospheric pressure plasma. 
 
     
     
       8. The method as claimed in  claim 1 , further comprising removing coating material in a region of the damaged location before said covering of the damaged location. 
     
     
       9. The method as claimed in  claim 1 , further comprising roughening or oxidizing the damaged location prior to covering the damaged location with the one or more materials. 
     
     
       10. The method according to  claim 1 , wherein the surface structure is arranged on the covering element and is configured to reduce directional reflection of ultraviolet or infrared radiation. 
     
     
       11. The method according to  claim 1 , wherein the covering element coating is arranged on the covering element and is configured to divert ultraviolet or infrared radiation from a beam path along which the reflective optical element reflects radiation at the operating wavelength. 
     
     
       12. A collector mirror for EUV lithography, comprising:
 a substrate and a mirror coating that reflects at an operating wavelength in a range of between 5 nm and 20 nm, 
 wherein the mirror coating comprises a covering element localized to a damaged location of the mirror coating, wherein the damaged location comprises delamination or blistering of the mirror coating, wherein arranged on the covering element is one or more of a surface structure, a convex or concave surface or covering element coating corresponding to the mirror coating, or a combination thereof. 
 
     
     
       13. The collector mirror as claimed in  claim 12 , wherein the covering element is embodied as a film or a covering unit. 
     
     
       14. The collector mirror as claimed in  claim 12 , wherein the covering element comprises one or more of the materials of the group metal, steel, high-grade steel, Invar, aluminum, molybdenum, tantalum, niobium, silicon, titanium, zirconium, hafnium, scandium, yttrium, lanthanum, cerium, copper, silver, gold, platinum, rhodium, palladium, ruthenium, glass, ceramic and aluminum oxide. 
     
     
       15. The collector mirror as claimed in  claim 12 , wherein the mirror coating locally comprises a covering coating. 
     
     
       16. The collector mirror as claimed in  claim 15 , wherein the covering coating comprises one or more of the materials of the group molybdenum, tantalum, niobium, silicon, titanium, zirconium, hafnium, aluminum, scandium, yttrium, lanthanum, cerium, oxides thereof, nitrides thereof, carbides thereof, borides thereof, gold, platinum, rhodium, palladium, ruthenium, carbon, boron carbide and boron nitride. 
     
     
       17. A method for repairing delamination or blistering of a coating of a reflective optical element for extreme ultraviolet (EUV) lithography which comprises a substrate and the coating that reflects at an operating wavelength in a range of between 5 nm and 20 nm, comprising:
 localizing a damaged location caused by the delamination or blistering of the coating; 
 roughening or oxidizing the damaged location; and 
 covering the damaged location with one or more materials by applying a covering element to the damaged location, wherein the covering element is localized to the damaged location, 
 wherein arranged on the covering element is one or more of a surface structure, a convex or concave surface or a covering element coating corresponding to the coating of the reflective optical element. 
 
     
     
       18. The method as claimed in  claim 17 , wherein the covering element is secured on the coating with adhesive. 
     
     
       19. The method as claimed in  claim 17 , wherein the covering element comprises one or more materials of the group metal, steel, high-grade steel, Invar, aluminum, molybdenum, tantalum, niobium, silicon, titanium, zirconium, hafnium, scandium, yttrium, lanthanum, cerium, copper, silver, gold, platinum, rhodium, palladium, ruthenium, glass, ceramic and aluminum oxide. 
     
     
       20. The method as claimed in  claim 17 , wherein said covering comprises applying a covering coating to the damaged location.